Showing what's behind the curtain

Find the sum of all the numbers that can be written as the sum of fifth powers of their digits.

Investigating combinations of English currency denominations.

Find the sum of all 1-9 pandigital numbers that is composed of two factors and their product.

Discover all the fractions with an unorthodox cancelling method.

Find the sum of all numbers which are equal to the sum of the factorial of their digits.

How many circular primes are there below one million?

Find the sum of all numbers less than one million, which are palindromic in both base 10 and base 2.

Find the sum of all eleven primes that are truncatable from both left to right and right to left.

What is the largest 1 to 9 pandigital that can be formed by multiplying a fixed number by 1, 2, 3, … ?

Find the value of p ≤ 1000 which produces the most integer right triangles.